Generally, in order to prevent the electronic device from being contaminated by particle or dust in the atmosphere, the electronic device is usually disposed in a closed housing. However, the electronic device will generate a lot of heat during the operating process. If the electronic device is continuously placed in a high-temperature state, it will easily cause a damage on the electronic device and shorten its useful life. Thus, in order to prevent the malfunction of the electronic device, a heat-dissipating fan is usually used to dissipate the heat generated by the electronic device from inside to external environment.
Please refer to FIG. 1A which is a top view of a traditional fan. This fan includes a hub 11 and a plurality of blades 12 arranged around the hub but each blade does not overlap with the other. The mold used for manufacturing such a fan is composed of a male mold 13 and a female mold 14 and the separating line between the male mold and the female mold is indicated by an imaginary line 15 shown in FIG. 1B. When stripping the mold, the male mold 13 and the female mold 14 are separated from each other along the upward and downward directions, respectively, indicated by the arrows shown in FIG. 1B to complete the manufacturing process.
At the present time, a commonly used way for increasing the airflow discharged from the fan so as to enhance the heat-dissipating efficiency is to enlarge the size of blades of the fan or increase the number of blades. However, under the design limitation of mold used for manufacturing the fan, the size or number of blades of the fan can not be effectively increased to improve the heat-dissipating performance of the fan.
With the improvement of technology, one way is to allow two blades to be disposed closely as possible so as to slightly increase the discharged airflow. However, this way will let the mold have an acute notch as an edge on a knife, which may be vulnerable or easily damaged.
Therefore, it is desirable to provide a heat-dissipating device which can greatly enhance the heat-dissipating efficiency.